Although he acted onstage in school plays and declared his intention to pursue that career when he enrolled at Harvard, Damon found it difficult at first. His initial screen appearance was in the one-line role of Adam Storke's younger brother in "Mystic Pizza" (1988). He was well-cast as Brian Dennehy's medical school dropout kid in the made-for-cable movie "Rising Son" (TNT, 1990) and excelled as an anti-Semitic preppie in "School Ties" (1992), but has stated that the competition for the roles in his age range was fierce. Nearly all the young men in "School Ties" had auditioned for the co-starring role in "Scent of a Woman" (also 1992), but the plum role went to Chris O'Donnell. In fact, Damon and O'Donnell often competed for roles with the latter generally winning out. While Damon proved adequate in the sizable role as the narrator of Walter Hill's revisionist Western "Geronimo: An American Legend" (1993), he and his role were outshone by more seasoned actors (i.e., Gene Hackman, Wes Studi). On the other hand, he all but stole "Courage Under Fire" (1996) from Denzel Washington, offering a vivid turn as a guilt-ridden veteran of the Persian Gulf War tormented by an incident in battle. (He lost forty pounds to achieve the gaunt, haunted look of the character.)

While at Harvard, Damon had begun to write a script about a troubled mathematics genius. With childhood buddy and frequent co-star Ben Affleck, he fashioned a screenplay that soon became the talk of Hollywood with studios bidding competitively for the project. In 1994, Castle Rock initially purchased the rights for over a half-million dollars in a pay-or-play deal. The story then focused on Will, a South Boston resident with superior intelligence whom the government attempts to recruit. A year later, with the project in turnaround, Miramax purchased the rights and the script had evolved to focus more strongly on the emotional difficulties of the leading character. Before "Good Will Hunting" went before the cameras, however, Damon landed his first screen lead as a newly-minted crusading attorney in Francis Ford Coppola's adaptation of "John Grisham's 'The Rainmaker'" (also 1997). The one-two punch of the two leading roles (undoubtedly assisted by the resulting publicity for Damon and Affleck as writers and actors) solidified the actor's status as the "It" boy of 1997. Earning both a Best Actor Academy Award nomination and sharing an Oscar win for Best Screenplay further raised his profile.

With his career in high gear, Damon was now in a class alone, no longer having to compete with Chris O'Donnell (whose own star was tarnished by "Batman and Robin"). Before the hoopla, Stephen Spielberg had tapped the actor to play the title role in the World War II epic "Saving Private Ryan" (1998), which critics heaped with praise for its showy camerawork and impressively staged battle set pieces. As the soldier whose three brothers have been killed in action, the All-American looking Damon was in only the last third of the film, but still managed to make an impression. He fared less well as the poker hustler-turned-law student who agrees to help his ex-con best friend in "Rounders" (also 1998). In this redux of Martin Scorsese's 1974 drama "Mean Streets," Damon relied more on his winning personality, warm smile and good looks than on his acting ability, giving more of a "movie-star" portrayal than a real performance. Still, he now had his pick of roles. Repaying writer-producer-director Kevin Smith for his assistance on "Good Will Hunting", he teamed with Affleck to play a pair of fallen angels trying to get back into heaven in "Dogma" (1999). Damon followed by undertaking the more challenging title role of an American who decides to murder his traveling companion (Jude Law) and assume his identity in Anthony Minghella's well-crafted "The Talented Mr Ripley" (also 1999), resulting in one of the actor's best, most intense performance, though the film largely built its reputation and devoted admirers after its initial release.

Damon's career hit a brief but worrisome slump with the release of three creative and box-office duds in a row: director Robert Redford's lethargic "The Legend of Bagger Vance" (2000) with Damon as a washed up golf pro opposite wise caddy Will Smith; "All the Pretty Horses" (2001), director Billy Bob Thornton's failed adaptation of novelist Cormac McCarthy's Western; and a small supporting turn in Van Sant's by-the-numbers "Finding Forrester" (2000). The actor recaptured his A-list cachet when he joined the all-star cast of Steven Soderbergh's remake of "Ocean's Eleven" (2001), playing pickpocket and aspiring big-time thief Linus Caldwell in the popular hit--he would return to the role for the sequel "Ocean's Twelve" (2004). His next film was a complete about-face from those slick, polished crowd-pleasers: Damon and Casey Affleck starred (and co-wrote) the largely improvised drama "Gerry" (2002), a little-seen effort directed by Van Sant about two men named Gerry who are stranded in the desert during a hiking mishap—an intriguing experiment but not for mainstream audiences.

Demonstrating his increasing diversity and believability, Damon took on the role of the amnesiac über-spy Jason Bourne in the film adaptation of Robert Ludlum's "The Bourne Identity" (2002), a crackerjack thriller that did solid box office business and became a mega-hit on home video. The actor would reprise the role for the equally well-crafted sequel "The Bourne Supremecy" (2004). And he would demonstrate a flair for goofball comedy, with a wickedly funny turn on the small screen as Jack's scheming rival to join the gay men's chorus in a 2002 episode of the hit NBC sitcom "Will & Grace," a role he was expected to reprise; and when he teamed with perfectly smarmy foil Greg Kinnear as a pair of conjoined twins in the Farrelly brothers' flawed but winning "Stuck On You" (2003).

His next film cast him opposite Heath Ledger as an utterly fictionalized version of Wilhelm and Jacob Grimm, the Bavarian fairy tale spinners known as "The Brothers Grimm" (2005), re-imagined by director Terry Gilliam as a pair of curse-removing con artists who are suddenly tasked with solving a genuine magical mystery that ultimately inspires many of their famous stories. Damon showed a great deal of panache and charisma as practical scoundrel Wilhelm, but the story ultimately left him too little to do, and the film lacked some of the spark and imagination expected of a Gilliam project (behind the scenes, Damon was also credited with frequently playing peacemaker between the embattled Gilliam and the films' producers, the Weinstein brothers). At the end of that year Damon gave a fine performance in the complex potboiler "Syriana" (2005) as an oil industry analyst living a comfortable life in Geneva with his family, but the death of one of his children while on a visit to an oil-rich nation drives him to become obsessed with helping the country's benevolent young prince raise his nation with sound business dealings.

Damon next joined an all-star cast that included Leonardo DiCaprio, Mark Wahlberg and Jack Nicholson for “The Departed” (2006), playing a hardened criminal employed by a crime syndicate who infiltrates the police while his counterpart (DiCaprio) on the force goes undercover in the mob. Based on the excellent Hong Kong action thriller “Infernal Affairs” (2002) and directed by Martin Scorsese, “The Departed” earned a huge helping critical kudos prior to its early October release. In “The Good Shepherd” (2006), an historical look at the beginnings of the CIA, Damon played Edward Wilson, a bright, idealistic Yale student recruited by the OSS during World War II to work intelligence. He later was one of the covert founders of the CIA, but became disenfranchised amidst the heightened suspicions and deep-rooted paranoia of the Cold War. After signing on to star in “Ocean’s 13” (lensed 2006), the third—and hopefully last—installment in director Steven Soderbergh’s caper franchise, Damon went to work on another sequel, “The Bourne Ultimatum” (lensed 2006), reviving master assassin Jason Bourne, who comes out of retirement to defeat arch rival, The Jackal, in a once-and-for-all showdown.